Method for measuring and analyzing surface roughness on semiconductor laser etched facets

Abstract

A scanning electron microscope is used to scan the etched facet edge to produce digital data representative of its profile. A Fourier transform of the edge profile is produced and the resulting plurality of spatial frequency components can be used to generate a first low frequency waveform component indicative of lack of precise edge definition, a midrange frequency component indicative of poor liftoff samples, and a high frequency component indicative of metal grain size. A tilt adjustment feature of the electron microscope is optionally used to advantageously magnify the shape of the profile in the y direction.

What is claimed is: 
     
       1. Method of measuring surface characteristics of a semiconductor facet having a surface profile comprising the steps of: (a) digitizing data representative of said surface profile to produce digitized data;   (b) taking the Fourier transform of said digitized data;   (c) taking the inverse Fourier transform of spatial frequency spectrum components resulting from the execution of step (b) and reconstructing three waveform components therefrom wherein:   (d) a first waveform component has a 10-30 micron period for measuring the extent of edge wander, a second waveform component has a 2-5 micron period for measuring the extent of bumpiness and a third waveform component has periods of less than two microns for measuring the extent of surface roughness.   
     
     
       2. The method of claim 1 wherein step (a) includes scanning said semiconductive facet with a scanning electron microscope having a given effective magnification. 
     
     
       3. The method of claim 2 including the step of increasing the effective magnification of said semiconductor facet in the y direction during the performance of step (a).